Camouflage covering

ABSTRACT

A covering for application on surfaces of a structure, includes at least one sheet including a plurality of components, each component being capable of protecting the structure against detection by at least one sensing method. The sheet can have an adhesive exterior surface whereby it can be adhered to the structure and wherein the exterior surface opposite the adhesive surface has an uneven surface profile.

BACKGROUND INFORMATION

Protecting a structure such as a building or a vehicle from detectionoften is desirable. Many means of camouflaging objects are known in thefields of surveillance and wildlife observation.

Some of these involve protection that is built-in to the structure inquestion. For example, GB 565,238 describes a process and means forcoating objects for the purpose of camouflage. A paint-like coating isapplied which protects the objects from detection in the visible andinfrared (IR) portions of the electromagnetic spectrum. This type ofbuilt-in camouflages is effective against visual detection only in areaswith natural color(s) that match closely those of the camouflage system.For example, a temporary building painted with a sand-colored coatingwould be camouflaged in desert situations but would stand out against ajungle environment; thus, the structure would require repainting whenmoved from one environment to another.

Other means involve removable protection such as, e.g., a camouflagenet. In this respect, U.S. Pat. No. 5,549,938 describes flexiblemagnetic panels having camouflage patterns provided thereon. The panelsare designed to magnetically attach to steel surfaces such as the panelsof a vehicle, reducing the chance of visual detection of the vehicle.Such removable camouflage panels are convenient to apply or remove butare designed to protect an object only against visual detection.Surveillance equipment or animals with the ability to detect UV or IRemissions, for example, can detect the presence of an object protectedby such panels.

Yet another means is a semi-permanent type, such as a demountable screenfor shielding. In this respect, U.S. Pat. No. 4,560,595 discloses acamouflage sheet material designed to have thermal emissioncharacteristics which match closely those of the natural environment inwhich the camouflage material is to be used. The sheet can protectobjects against detection in the thermal IR wavelength ranges and isalso adapted to provide camouflage in the ultraviolet (UV), visible andphotographic IR wavelengths. The camouflage material may be attached toa supporting web by means of an adhesive or by mechanical means such asclamps or sewing. This type of sheet material cannot be applied easilyand quickly to a structure because it first must be attached to asupporting web and then somehow attached to a structure to be protected.If the structure is, e.g., a vehicle, the sheet must be securelyattached to the vehicle to prevent it from releasing when the vehiclemoves.

It is often important that a camouflage covering be robust againstsevere weather and remain in place and undamaged for extended periods oftime.

A brief discussion will now be given of sensing methods available fordetecting objects, and of protection means available to protect againstdetection.

Detection in the visible portion of the spectrum is used, both byland-based surveillance systems or individuals and by satellites, todetect the presence of objects. The nature of an area surrounding anobject dictates the type of camouflage cover required to protect againstvisual detection. The earlier examples of desert and jungle situationswould require sand-colored and patterned green coverings respectively.It is often desirable that the color of a surface change rapidly for acamouflage system to adapt to new surroundings.

Similarly, the surface texture of an object can affect whether an objectis easy or difficult to detect visibly. Surface profiling can be used toprotect objects against detection by aerial imaging. If a surface of anobject is uneven, light scatters unevenly (i.e., differently fromdifferent parts) thus breaking up the lines of the object and renderingit difficult to detect. Shadows created by an object also can beminimized by suitable use of uneven surface profiles.

The shape of objects also can be important. Many vehicles and buildingsare designed to have stealthy shapes comprising multiple oriented flatpanels which are not easily detected. An irregularity in the shape of asurface can render the surface susceptible to detection. For example, abolt protruding from an otherwise smooth surface can give a strongsignal on imaging equipment in certain parts of the electromagneticspectrum.

UV sensors can detect an object that transmits a UV signaturesubstantially different from that of its surroundings. UV pigments canbe used to give the surface of an object the correct properties suchthat it cannot easily be observed by UV sensors.

In an analogous manner, IR signatures of objects can make them easy todetect, and pigments again can be used to give an object apparentlysimilar IR properties to that of its surroundings. Alternatively,reflective metallic layers can be incorporated beneath a colored but IRtransmissive polymer (e.g., polyethylene or polypropylene) film.

Thermal imaging can be used to detect objects via the (IR) heat thatthey produce. Metallized particles or fibers (scrim) incorporated into amaterial, or a metallized film applied over the same, can be used toreflect heat produced in the object back toward the source so that theexternal surface of the object is not seen as producing a great deal ofheat. An example of a situation in which this effect might be useful isin protecting a moving vehicle from detection while the engine of thevehicle radiates a large amount of heat.

In addition, or alternatively, phase change materials (PCMs) can be usedto absorb heat from hot spots of objects. For instance, a PCM whichoperates at a high temperature could be used to smooth out the heatsignature of a boiler housing.

Radar is also used in surveillance systems to detect objects. To avoiddetection by this method, radar-absorbing materials (RAMs) can be usedin camouflage coverings.

Absorption of acoustic signals also often is desirable. Materials suchas high density foam, rubber and ceramics can be effective for thispurpose.

Providing a camouflage covering that can be applied quickly, easily andsecurely to an object to be protected and that can provide protectionagainst a range of detection means remains desirable.

SUMMARY OF THE INVENTION

Briefly, the present invention provides including at least one sheethaving a plurality of components, each component being capable ofprotecting a structure against detection by at least one sensing method.The sheet has an adhesive exterior surface whereby it can adhere to thestructure and, opposite the adhesive surface, an exterior surface withan uneven surface profile.

A backing sheet can be removably attached to the adhesive surface suchthat the backing sheet can be removed to expose the adhesive surface.The covering then can be applied directly to a surface of an object tobe protected. The covering subsequently can be removed from the objectwithout damaging it.

The covering can include UV and/or IR pigments. Also, it can include ametallized scrim, the threads of which could be metallized with Al, Ni,Cu, or chrome.

The covering can include one or more radio absorbing material such ascarbonyl iron, aramid fibers, ferrites, or carbon loaded foams. Suitableclasses of RAMs include Salisbury screens, Jaumann absorbers, circuitanalog absorbers, magnetic RAM and Hybrid RAM systems. Additionally, thecovering can include a flexible soft-magnetic thin film which can act asboth a radar absorber and an IR reflector. Suitable examples of magneticfilms include alloys of Co, Fe, Si, Mo, and Bo and/or Co, Zr, and Nb.One component of the covering could suitably comprise a PCM such ashydrated AlCl₃, hydrated MgCl₂, or Glauber's salt.

The covering also can suitably include an acoustic absorber made of amaterial as described previously.

The sheet preferably is flexible so that it can be rolled up for easytransportation, storage, application and manipulation.

The covering can include a plurality of layers each provides protectionagainst detection by at least one sensing method. One of the layers canbe a paint layer applied directly to the object to be protected or to asurface of the covering itself. Suitably, at least one of the layers ofsuch a multilayer covering can be removably adhered to an adjacentlayer. Adhesive layers could be provided between each of the layers.This convertibility/removability feature of might be useful insituations where altering the visual appearance of a covering whileleaving the other camouflage functions of the covering unchanged isrequired. For example, a sand-colored upper layer could be removed froma covering at a time when the covering is no longer to be used in adesert environment but is instead to be used in a vegetated area. Thiscan eliminate the need to remove the entire covering, which may still bein good condition after extended use; instead, the outer layer could bepeeled off and replaced by a similar outer layer of a different patternor color to suit the new environment.

According to a second aspect, the present invention provides a methodfor protecting a structure. The method includes applying to a surface ofthe structure a covering having any combination of the features as setout above in relation to the first aspect of the invention.

According to a third aspect, the present invention provides a camouflagesystem that includes first and second coverings as just described withthe second covering being removably adhered to the first.

In a fourth aspect, the present invention provides a kit forcamouflaging surfaces that includes a first elongate sheet patternedwith two zones, the zones having different appearances, each zoneextending along a relatively long dimension of the sheet, wherein oneside of each zone runs continuously along a respective side of thesheet, and the other side of each zone is delimited by a boundaryextending along the relatively long dimension of the sheet in agenerally undulating form. All regions of the sheet on one side of theboundary form a zone of a first appearance and all regions of the sheeton the other side of the boundary form a zone of a second appearance;and a second elongate sheet having a continuous field of the firstappearance within which are disposed isolated regions of the secondappearance. The two sheets can be subdivided with resulting sectionsfrom each being capable of being joined so as to form a camouflagepattern.

In yet another aspect, the present invention provides a method forforming a covering for application on surfaces of a structure. Themethod includes digitally printing a non-repeating camouflage patternonto a covering having any one or more of the features set out above.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, like reference numerals refer to likeparts.

FIG. 1 shows a cross section of a camouflage covering according to thepresent invention which includes several components.

FIG. 2 shows a camouflage covering that includes an adhesive surfacewith a removable backing sheet.

FIG. 3 shows an unprotected building exposed to light.

FIG. 4 shows a building protected by a camouflage covering being exposedto light.

FIG. 5 shows the heat signature of an unprotected boiler house.

FIG. 6 shows the heat signature of a boiler house protected by acovering comprising a PCM and metallized scrim.

FIG. 7 shows two sheets including multi-zone patterns in accordance withthe fourth aspect of the invention described above.

FIG. 8 shows portions cut from the sheets from FIG. 7.

FIG. 9 shows the combination resulting when the strips from FIG. 8 arecombined.

DETAILED DESCRIPTION

FIG. 1 shows covering 1 with several components 10-15, each of which canprovide protection against detection for a covered object. Anycombination of the components shown may be used in a camouflagecovering; other components having similar or different camouflageproperties can be incorporated in a similar manner.

Component 10 is a painted or printed layer. The layer may be patterned,and is of one or more colors that provide limited contrast with thesurroundings of the structure to which covering 1 is to be applied. Thepattern of the painted or printed layer is intended to make difficultvisual detection of a structure within a pre-decided (visible)wavelength range.

Further layers of paint or adhesive printed sheets may be applied tolayer 10 to change the color of the covering to match differentsurroundings. Layer 10 may be digitally printed to give a camouflagecolor and pattern most suited to a specific operational environment. Thecolor and pattern could be generated from a set of real backgroundimages by, for example, analysis of such images to establish a form ofpattern that has low contrast against the background and then formingimages of that form by means of a suitable algorithm or pseudo-randomprocedure. Covering sheets could be individually printed for disguisingspecific objects against their backgrounds. With digital printing,sheets can be printed with a non-repeating pattern, which can make thesheets less prone to detection.

Component 11 is a surface which has been embossed to give a profiledstructure. The profiled structure has a degree of surface relief and/orunevenness which acts to scatter light and other electromagneticwavelengths from the covering to break up the outer surface of astructure to which the covering is to be applied. Embossed surface 11 isuseful in protecting a structure against detection by visible (aerial),IR and RADAR imaging.

The dimensions of the indentations determine the frequencies ofradiation against which the covering can best protect. Preferably, thedimensions of the features of the surface profile—the depth of grooves,the height of protrusions, and/or the spacing between them—areapproximately half the wavelength of the radiation against whichprotection is desired. If, for example, protection against IR detectionis desired, the features of the surface relief should be of the order of0.4 to 500 μm, e.g., 200 μm.

Additionally, the surface profile can be used to disrupt the shadow of astructure. For this purpose the dimensions of the features of thesurface relief should be of a scale of approximately 1 to 50 cm. Therelief could be provided by an array of comb-like projections from thesurface of the covering.

To deflect radar, the surface indentations should preferably beregularly shaped, and around 1 mm deep. Again, preferably the dimensionsof the features of surface relief are approximately half the wavelength.

Component 12 contains UV and/or IR pigments which provide the surface ofa protected structure with UV and/or IR signatures resembling those ofits surroundings, thus protecting the structure against detection by UVand/or IR sensors. Alternatively, a metallic film positioned beneath apigmented, IR transmissive film can be used to the same effect.

Component 13 includes a PCM which preferably changes phase at a workingtemperature in such a way that the phase change is endothermic uponincreasing temperature. In this way, the PCM acts as a thermal buffer.Preferably, the working temperature of the material is around the upperor lower limit of the expected ambient temperature at the location wherethe covering is to be used. Layer 13 acts to absorb heat when it reachesthe phase change temperature of the PCM, thus smoothing out the heatsignature of structures containing heat-producing objects.

Component 14 is a metal film which assists heat dissipation. This alsoacts to smooth the heat signature of the structure being protected, byreflecting heat towards the source and thus preventing the externalsurface of the structure from producing a localized heat signature.

The points 15 shown in FIG. 1 represent the cross sections of metallizedthreads, or scrim, woven into covering 1. When a covering comprisingscrim is applied over an outer surface of a structure, an effect of thescrim is to produce a Faraday cage. The inside of the structure must beelectrically uncharged, such that any charge placed inside the cage iscancelled by an equal and opposite charge spread across the exterior ofthe cage. A structure protected by a scrim covering is thereforedifficult to detect by means of electromagnetic imaging in that itprevents transmission of EM waves in or out of the structure. Inaddition the scrim should protect the structure from an electromagneticpulse. The scrim also acts to reflect heat produced within thestructure.

Such metallized threads can be produced by electrocatalytic depositionin which a thin layer of Cu or Al is deposited onto the surface of afiber. As discussed above, metallized particles or a metallized film canbe used in place of scrim.

An adhesive layer 16 is shown on an exterior surface of covering 1. Thisallows covering 1 to be applied quickly and easily to an object to beprotected. The adhesive 16 could be covered by a removable backing sheetto protect the adhesive layer prior to application of the covering.

In FIG. 2, layer 17 is a backing sheet removably adhered to covering 1.This backing sheet can be peeled off for covering 1 to be adhesivelyapplied to the surface of a structure/object.

FIG. 3 shows a building 20, such as a temporary structure erected from aflat-pack, unprotected by any camouflage covering. Building 20 isexposed to light from, say, the sun or a spotlight. The surface 22 ofthe building, which is shaded from the light, appears considerablydarker than surface 21, which is directly exposed to the light source.This contrast in shadow allows building 20 to be detected easily by anequipment or individual scanning in the visible range of the spectrum.

To reduce this susceptibility, use can be made of embossed surfaces (11in FIG. 1) which act to scatter light and create shadows on surfaces ofthe structure to be protected. The result of this effect is shown inFIG. 4 where it can be seen that surface 21 appears darker than in FIG.3, and surface 22 appears relatively lighter.

FIG. 5 shows a boiler house 30 without any camouflage covering. A boileris contained within the structure, and its location is shown at 31. Heatemitted by the boiler produces a heat signature as represented bycontour lines 32. The source of the heat can clearly be seen, and thissignature of the boiler house is in sharp contrast to the heat signatureof the natural environment in which the boiler house is situated. Thisrenders the boiler house susceptible to detection by heat sensingsurveillance equipment.

If a covering including a PCM (shown as 13 in FIG. 1) is used to protectthe boiler house, the heat signature of the structure changes; FIG. 6shows this smoother signature. A small heat source positioned at 31still can be seen within boiler house 30, but the contour lines 33 areconsiderably more separated from one another than before, which makesdetection by IR scanning methods less likely.

A high performance thermal insulating layer also can be included in thecovering. Suitable materials for this layer would include glass fibre,microfiber or aerogels.

The inclusion in a camouflage covering including more than one of thecomponents discussed above provides simultaneous protection fromdetection by multiple sensing methods. In addition, an adhesive surfaceallows the covering to be applied quickly and easily to a structure. Itmay also be adapted such that, upon removal of the covering, theunderlying structure is undamaged and may subsequently be covered by adifferent covering. This feature would be useful in circumstances wherestructures are required to be frequently erected and dismantled.

The covering is conveniently in sheet form. The sheet may be formed ofone or more sub-sheets laminated or adhered to one another. Thesub-sheets may be bonded together either permanently or releasably by anadhesive layer carried by one or both of the sub-sheets.

In a preferred arrangement, one such sub-sheet includes one or morecomponents that can inhibit detection by a sensing means such as radaror IR scanning (the effectiveness of which is relatively independent ofthe environment in which the covering may be deployed) and anotherincludes one or more components that can inhibit detection by a sensingmeans such as visible observation (the effectiveness of which isrelatively dependent on the environment in which the covering is to bedeployed). With this system, the former sub-sheet can be applied to astructure for protection in any environment. A number of variations ofthe latter sub-sheet can be available for use in correspondingenvironments, e.g., desert, temperate, jungle, snow, etc. The lattersub-sheet is preferably deployed on the outside of the covering, furtherfrom the outer surface of the object to be protected so that its surfaceis exposed once the sheet has been deployed. Three or more sub-sheets,each with respective protective properties can be used.

The inner and outer sheets each can be provided with an adhesive layeron one of their major surfaces. In the case of the inner sheet, this canbe used for attaching it to a structure that is to be protected; in thecase of the outer sheet, this can be used for attaching it either tosuch a structure or to an inner sheet that has previously been adheredto the structure. The adhesive layer of the inner sheet could employ apermanent adhesive while the adhesive layer of the outer sheet couldemploy a releasable adhesive, or the adhesive layer of the inner sheetcould be more adherent than that of the outer sheet. Theseconfigurations make it easier to apply an inner sheet to a structure andthen change its appearance to match a certain environment by removing apreviously deployed outer sheet and replacing it with another. Amultiplicity of such inner sheets can be used, one on top of another, toprovide additional protection.

The sheet(s) can be fitted with a removable protective sheet over thefor the reasons stated previously.

The components that help to provide protection can be formed into asheet or layer, embedded into a sheet, and/or sandwiched between twosheets depending on the nature of the components.

The sheet(s) can be formed from a polymer such as PVC, PVF,polypropylene, polyethylene, silicones, polysulfones, polyesters, andthe like.

FIG. 7 shows a pair of sheets of a covering. The sheets are relativelylong in one dimension and may be rolled up for storage and easytransportation in the same way as conventional wall paper. Each sheet,70 and 75, is patterned with two zones. Each zone has a single color ormulticolored pattern; for example, zones of the first type may becolored green, and zones of the second type colored brown.

Sheet 70 is patterned such that zone 72 extends along the longerdimension of the sheet. One side of zone 72 runs continuously along oneside of sheet 70; the other side of zone 72 is delimited by boundary 73extending along the longer dimension of the sheet in a generallyundulating form. All regions 71 of the sheet on the other side ofboundary 73 form a zone of the second type. Sheet 75 has a field 76formed by a zone of the second type on which are disposed isolated zones78 of the first type, shown as approximately oval.

Referring now to FIG. 8, if portions of sheets 70 and 75 are applied ina particular way to an object to be camouflaged, then a useful patterncan be obtained. Strips 80 and 82 of sheet 70 are applied along oppositesides of a surface of the object so that the zones 72 of the first typeof those strips run along the edges of that surface. The region betweenthose strips is filled with strip 81 from sheet 75. The arrangement ofstrips 80, 81 and 82 is shown in FIG. 8, and FIG. 9 shows an overallpattern resulting from such a combination.

The effect of such a pattern is that the sides of the surface alongwhich the zones of the first type (strips 80 and 82 from FIG. 8) run canbe camouflaged especially effectively. For example, if the color and/orpattern of the first zone of is of low contrast with the surroundings ofthe object, then the presence of a zone of the first type continuouslyalong two sides of the object is likely to make it more difficult todetect. For example, in a woodland setting, if the zone of the firsttype is dark (e.g., black), then it can visually disrupt the edges ofthe object by causing confusion with nearby shadows.

A preferred configuration is shown in FIG. 9 in which the wavy boundary73 (from FIG. 7) periodically defines wider regions of the zone of thefirst type, and these regions are located at the corners of the surfaceof the object on which the sheets are applied. This can emphasize thevisual disruption at the corners of the object.

In this way, large surfaces can be covered with an effective camouflagelayer without the necessity of large individual sheets. Large sheets aredifficult and cumbersome to manipulate and store.

Sheets 70 and 75 could suitably be coated on the side opposite thepatterned side with an adhesive layer, and the adhesive layer couldconveniently be covered by a removable backing sheet. This allows forsimple and quick application of the sheets in any desired arrangement.

Each individual feature has been described in isolation, but anycombination of two or more such features also is to be considered ashaving been disclosed, to the extent that such features or combinationsare capable of being carried out based on the present specification as awhole in the light of the common general knowledge of a person skilledin the art, irrespective of whether such features or combinations offeatures solve any problems disclosed herein. Aspects of the presentinvention may consist of any such individual feature or combination offeatures.

1. A covering for application to one or more surfaces of a structure,the covering comprising a sheet including a plurality of components,each of said components being capable of providing protection againstdetection by at least one sensing method, said covering having anadhesive exterior surface and an exterior surface opposite the adhesivesurface having an uneven surface profile, said covering optionallyfurther comprising a backing sheet removably adhered to the adhesiveexterior surface.
 2. The covering of claim 1 wherein said at least onesensing method comprises visible inspection, surface profiling,ultraviolet sensing, infrared sensing, thermal imaging, radar andacoustic.
 3. The covering according to claim 1 wherein at least one ofthe components comprises at least one of an ultra-violet pigment, aninfrared pigment, a metallic film, and metallized threads.
 4. Thecovering according to claim 3 wherein at least one of the componentscomprises a metallic film and a second component adjacent the firstcomponent comprises an infrared transparent polymer.
 5. The covering ofclaim 1 wherein at least one of the components comprises a radioabsorbing material.
 6. The covering of claim 1 wherein at least one ofthe components comprises a phase change material.
 7. The covering ofclaim 1 wherein at least one of the components comprises an acousticabsorber.
 8. The covering of claim 1 wherein said covering is flexible.9. The covering of claim 1 wherein said covering is printed with animage representing an environmental background.
 10. A system forcamouflaging surfaces comprising: a first elongate sheet patterned withtwo zones, the zones having different appearances, each zone extendingalong a primary dimension of the sheet, wherein one side of each zoneruns continuously along a respective side of the sheet, and the otherside of each zone is delimited by a boundary extending along therelatively long dimension of the sheet in a generally undulating form,such that all regions of the sheet on one side of the boundary form azone of a first appearance and all regions of the sheet on the otherside of the boundary form a zone of a second appearance; and a secondelongate sheet having a continuous field of the first appearance withinwhich are disposed isolated regions of the second appearance, each saidfirst and second elongate sheets being capable of being sectioned withthe resulting sections being capable of being joined to other sectionsso as to form a camouflage pattern.